1. Field of the Invention
The present invention relates to a display apparatus, more particularly, an image display apparatus.
2. Related Art Statement
As a conventional image display apparatus, the image display apparatus shown in FIG. 51 is disclosed in Japanese Patent Application Laid open No. 113,308/92. In this apparatus, a liquid crystal panel 2 for controlling a polarizing direction and a quartz plate 3 are arranged in front of the displaying surface side of a display liquid crystal panel 1 to display an original image in which the number of pixels in the horizontal direction is twice as the number of pixels of the display liquid crystal panel 1. To this end, in this image display apparatus, image signals in one image plane are thinned out every one pixel in the horizontal direction by a distributor 4 to decompose into images of two fields and to store them in frame memories 5 and 6. Images of respective fields stored in the memories 5 and 6 are read out every field with the use of a synchronous signal generator 7 and supplied and displayed on the display liquid crystal panel 1. At the same time, a required voltage is selectively applied to the liquid crystal panel 2 by a drive voltage generator 8 operated in synchronism with the read out of the image.
That is, in case of displaying the field image stored in the frame memory 5, a voltage is applied to the liquid crystal panel 2 for controlling a polarizing direction, and the image displayed on the display liquid crystal panel 1 is transmitted without rotating its rotating (polarizing) direction, and further transmitted to the quartz plate 3 as an ordinary ray, so that viewing the display liquid crystal panel 1 from the side of the quartz plate 3, as shown in FIG. 52A, the image is displayed at an ordinal pixel position (first position) of the display liquid crystal panel 1. In case of displaying the field image stored in the frame memory 6, also the applied voltage to the liquid crystal panel 2 is made off-condition and the image displayed on the display liquid crystal panel 1 is rotated by 90.degree. in its polarizing direction and transmitted to the quartz plate 3 as an extraordinary ray, thereby, as shown in FIG. 52B, displaying the image at the position in which respective pixels of the display liquid crystal panel 1 are shifted by a 1/2 pixel pitch in the horizontal direction from the ordinal pixel position, (second position), viewing the display liquid crystal panel 1 from the side of the quartz plate 3.
In this way, in the conventional image display apparatus shown in FIG. 51, one image plane is divided into two fields, a first field is displayed at the first position and a second field is displayed at the second position; this operation is performed with high speed, thereby interpolating the distance between pitch of pixels of the display liquid crystal panel 1 in the horizontal direction, as shown in FIG. 52C, resulting in an improvement of resolution.
In the liquid crystal panel, however, as a pixel array suitable for displaying the image, generally, a pixel array, referred to as a delta array, in which pixels are disposed by shifting there every line so as to interpolate pixels in the horizontal direction, is commonly utilized, so that even by adopting, in such a delta array, the above method of interpolating the distance between pitches of pixels, resolution can not be improved.
In the above conventional display apparatus, also, the quartz plate 3 is utilized to shift the pixel position to be observed by 1/2 pixel pitch, selectively, so that the working becomes difficult and thus the cost becomes high. Furthermore, the apparatus becomes large.
Moreover, in displaying the image on the liquid crystal panel, generally, the pixels arrayed in matrix are raster-scanned and also the liquid crystal has a memory effect in which afterimage occurs, so that as in the above conventional image display apparatus, if the pixels are shifted and displayed every field, for example, if the pixels are shifted from the first position to the second position and displayed, the first field image at the first position is displayed on the second field non-displayed region at the second position by the memory effect of liquid crystal, thereby decreasing resolution. Therefore, required object can not be attained.
As in the above conventional example, if image signals in one picture plane are divided or decomposed into two field images to interpolate pixel pitches, two expensive frame memories are required, so that the cost of whole apparatus becomes high.
Such a problem arises in the same manner as the above, even if display elements, such as plasma display, EL, photochromics or the like having pixels arrayed in matrix are utilized, as long as the case that images are displayed with the use of liquid crystal.